The main components of a motor vehicle drivetrain are a drive motor and a transmission. A transmission converts torques and speeds and so transforms the traction force provided by the motor drive. The present invention concerns a method for the operation of a drivetrain which comprises at least a motor drive and an automatic transmission. In the context of the present invention, the term “automatic transmission” is understood to mean any transmission that effects automatic gear changes, these also being known as variable-speed transmissions.
From DE 100 35 479 A1, a method for operating an automatic transmission is known in which successive upshifts and successive downshifts can be carried out with some overlap in order to improve the shifting speed. For this, during each first upshift or downshift, a shift element needed for the subsequent second upshift or downshift is prepared while the first upshift or downshift is in progress such that when a synchronization point, namely a synchronous speed of the first upshift or downshift in progress, is reached, the subsequent second upshift or downshift can be carried out immediately.
In this way, according to DE 100 35 479 A1, single shifts are overlapped with one another, which means that each first upshift or downshift carried out and each subsequent second upshift or downshift is a single shift between two directly successive gears.
The method, known from DE 100 35 479 A1, can be used with an automatic transmission comprising five shift elements of which, for transferring torque and force in each forward gear and in a reverse gear, two shift elements are engaged and three shift elements are disengaged. With such an automatic transmission six forward gears can be engaged. In the development of automatic transmissions, however, there is a trend is perceptible towards constantly increasing the number of gears, in particular, forward gears of the automatic transmission. Thus at present, automatic transmissions with eight forward gears and one reverse gear are being developed and such automatic transmissions have at least five shift elements to transfer torque or force, three of these, at least five shift elements, are engaged in any forward gear and in a reverse gear while the other two shift elements are disengaged. For such an automatic transmission, the method, known from DE 100 35 479 A1, is not suitable.
Starting from this, the present invention addresses the problem of providing a new type of method for the operation of a drivetrain comprising at least an automatic transmission and a motor drive.